The present invention relates to novel modified polyester resins. The resins comprise typical polyester-forming polyols, polyester-forming multi-functional acids or derivatives thereof, and, optionally, fatty oils or unsaturated fatty acids, in conjunction with specifically defined imide or amide moieties. The imide or amide moieties are prepared from a defined class of alkanolamines. Specifically, the compositions of the present invention comprise an imide or amide moiety which is derived from a branched primary alkanolamine.
The modified polyesters of the present invention may be referred to as "polyesterimides" and "polyesteramides"; however, it will be understood that the imide or amide moieties may be incorporated into the main polymer chain or may be pendent to the polymer chain.
The compositions of the present invention find use as coating resins, as binders for flexographic inks, etc. More specifically, certain of the resins of the present invention are useful in the preparation of coatings for metal substrates, e.g., as primer compositions, etc.
In the coatings industry there is a desire for compositions which are capable of air drying in short periods of time and without the necessity of high temperatures which require increases in energy expenditures. In an attempt to accomplish this goal, the prior art has taught the use of resins which have been end-capped with benzoic acid so as to improve the drying properties of coating resins without significantly increasing the molecular weight thereof. However, such resins have proven to be undesirably brittle when cured. Furthermore, it is desirable that coating compositions have a high solids content. Prior art resins have been incapable of providing the combination of high solids and good air-dry properties. In contrast to the prior art, it has now been found that the resins of the present invention which comprise an imide or amide moiety derived from a primary branched alkanolamine are capable of providing a uniquely advantageous combination of these desirable properties.
Polyesteramides and polyesterimides are known in the art as a general class of compounds. These resins exhibit a broad range of properties depending upon the specific composition of the material. Certain of the polyesterimides disclosed in the art have found utility as electrical insulations, such as in insulation varnishes. Polyesterimides which are useful in such applications must exhibit good heat resistance and are generally highly crystalline. An example of such resins can be found in U.S. Pat. No. 4,375,528, which discloses imidized polyesters which incorporate units derived from organic diamines. The organic diamines are preferably aromatic amines such as methylene dianiline, oxydianiline, phenylene diamines, etc. This patent neither discloses nor suggests the use of alkanolamines, and the resins disclosed therein do not exhibit the advantageous properties of the resins of the present invention.
U.S. Pat. No. 4,069,209 also discloses synthetic resins which are suitable for use as electrical insulation materials. The resins comprise aminodicarboxylic acids which are prepared from amino acids and tri- and tetracarboxylic acids, such as trimellitic acid, pyromellitic acid, and the anhydrides thereof. Again, the compositions of the present invention are neither disclosed nor suggested by this patent; there is no teaching of the inclusion of an imide or amide moiety derived from a branched primary alkanolamine.
U.S. Pat. No. 3,729,446 discloses imido-substituted polyester compositions which can be employed as coatings, varnishes, injection molding compounds, etc. These compositions are characterized as having at least one chemically combined aliphatically unsaturated imido radical. Again, however, the disclosed radicals do not comprise a primary imido group and a branched alkyl chain, as do the resins of the present invention.
U.S. Pat. No. 4,245,086 discloses the reaction product of trimellitic anhydride and a monoalkanolamine. The patent further discloses the polycondensation product of such a compound. The polymer is useful in the form of fibers, woven cloths, knitted cloths, films, sheets, and molded products. Again, this reference neither discloses nor suggests the resins of the present invention which contain ester linkages.
Defensive Publication No. 673,959, published Sept. 30, 1969, discloses highly polymeric linear condensation polymers prepared from 2,2-dimethyl-5-aminopentanol-1 and at least one bifunctional carboxy compound or derivative thereof. These products are amorphous, non-crystallizable polymers which are useful in the production of molded objects, sheeting, film, and hot-melt adhesives. The resins disclosed in this publication are thus two-component polymers which do not include polyol moieties therein. Furthermore, the compositions of the publication are not useful as coating compositions and do not provide the unique advantages provided by the compositions of the present invention.
Thus, there is provided by the present invention a class of polyesterimides and polyesteramides which have not been disclosed in the prior art. These resins are useful in the preparation of coating compositions, flexographic inks, etc.